The Geologic Time Scale Flashcards
Refers to the divisions of earth’s history based on life forms
Geologic Time Scale
are the largest intervals of geologic time with duration of hundreds of millions of years. The geologic time scale is divided into 4 major units
Eon
The geologic time scale is divided into 4 major units
Hadean Eon
Archean Eon
Proterozoic Eon
Phanerozoic Eon
there were fewer life forms. These life forms are more difficult to identify and the rocks have been disturbed often. An informal name given to the first three eons of the geologic time scale
precambrian
began 4.5 to 4 billion years ago. Known as the rock less eon. Except for the meteorites, no existing rocks on Earth today are from the Hadean eon. During this time, Earth was molten, and it would only solidify as it cooled.
hadean eon
began 1.5 billion years ago. during the Archean eon that single-celled organisms, such as blue-green algae, archeans, and bacteria, first appeared. It is the beginning of free oxygen in the atmosphere.
archean eon
the first era of the Archean Eon of the geologic record. Earth’s surface was dominated by volcanic activity during this era. The atmosphere consisted mainly of carbon dioxide and water vapor.
eroarchean era
The earliest confirmed evidence of life comes from this era, and Vaalbara, one of Earth’s earliest supercontinents, may have formed during this era.
paleoarchean era
the beginning of the Pongola glaciation on earth, which occurred in what is now South Africa. This was the first climate disaster on earth, as ice sheets covered areas of Swaziland and South Africa.
mesoarchean era
represents a key period in Earth’s evolution, as it recorded a transition in tectonic style, from an Early-Archean Earth dominated by episodic-overturn/stagnant-lid regime to a Proterozoic Earth in which modern- style Plate Tectonics became progressively established.
neoarchean era
began 2.5 billion years ago and ended 542 million years ago. the first continents appeared. This was also the time when continents merged into a single landmass called Rodinia. The Proterozoic eon is marked by the appearance of multicellular animals like sponges and the mass extinction of these organisms.
proterozoic eon
had given rise to crown eukaryotes, which are the ancestral organisms from which all modern eukaryotic lineages have evolved. This era is also marked by the earliest global-scale continent-continent belt collisions known.
paleoproterozoic era
are the breakup of the Columbia supercontinent, the formation of the Rodinia supercontinent, and the evolution of sexual reproduction. This era is marked by the further development of continental plates and plate tectonics.
mesoproterozoic era
is characterized by the most important climatic, tectonic and paleo - evolutionary changes in the Earth’s geological record
neoproterozoic era
The first life forms with parts, such as shells, scales, and bones and teeth, appeared during the Phanerozoic eon. The fossils of these life forms are great tools in the study of the history of the Phanerozoic eon.
phanerozoic eon
means “ancient life”. The supercontinent Pangaea was formed during the this era.
paleozoic era
represents the major increase in number of invertebrates.
cambrian to ordovician period
represents the evolution of fishes.
silurian to devonian period
represents the evolution of amphibians.
carboniferous to permian
means “middle life”. It’s a popular time division because it was when dinosaurs dominated and lived on dry land.
mesozoic era
came after a recent extinction that left only a few animals. One of these animals, the Archosaur, became the prototype for the dinosaurs in the Jurassic and Cretaceous period. Today, the only known descendants of Archosaurs are birds and crocodile-like animals.
triassic period
was the Golden Age of dinosaurs. Animals from the Triassic grew, spread and diversified in the Jurassic Period, making some of the most famous dinosaurs we know now today, like the T-rex. Some dinosaurs began to develop feathers, bone structures that resembled modern-day birds. This was a period when reptiles ruled all areas: land, water and air.
jurassic period
marks the final period of the Mesozoic era, when all living beings reached big and great sizes, but also faced harsh competition.
cretaceous period
recent life’. this era comes directly after the Mesozoic era. This era is well-known for introducing flowering plants, birds, insects and mammals, including humans.
Cenozoic era
abruptly when a meteorite slammed into the earth, leading to a mass extinction that wiped out about 75% of all species on Earth. This left only a few surviving mammals and reptiles that grew to be the animals we know now in modern day.
tertiary period
“old recent”
was the complete absence of dinosaurs and other reptilian groups
rapid proliferation and evolution of mammals
warm and humid climate
continents moved closer to their current positions
paleocene epoch
”dawn of the recent”
marks the first appearance of fossil
global climate is warm and rainy
noted for the expansion of mammalian stocks
eocene epoch
”few recent forms”
a global expansion of grassland and forest region
sudden decrease in earth’s temperature
noted for the expansion of mammalian stocks
oligeocene epoch
”less recent”
warmer global climate than the previous epochs
many fauna and flora died and others adapted to the drying world
miocene epoch
”continuation of the recent”
global climatic cooling
growth of mountains
animals flourished, other species died out
pliocene epoch
marks the time when humans started growing and thriving until present.
quaternary period
the “Great Ice Age”
the last time great diversity mammals lived like the mammoth
pleistocene epoch
the ”Age of Man”
All recorded human history occurred in this epoch
halocene epoch